The invention relates to a novel apparatus for desalinating saltwater in an ocean environment by utilizing solar energy. With an increasing amount of offshore work, particularly in the petroleum industry, there is a growing need for a safe, economical, and efficient way of producing large quantities of fresh water from the abundance of available saltwater. The apparatus disclosed will not only produce an abundant amount of fresh water from saltwater, but it will operate entirely off solar radiation.
Presently, the offshore industry must either transport the fresh water from onshore via supply boats or pipelines or chemically treat saltwater at the offshore site. Either method is very expensive, particularly the latter which requires an enormously large amount of chemicals for obtaining the required quantity of fresh water on an industrial scale. While the existing practices exhibit some utility, the industry has always felt there was a need for significant advancement.
Distillation of saltwater by solar heat is well documented in the prior art. However, the disclosure relating to offshore distillation have catered to emergency units utilized in distress situations. Fox, U.S. Pat. No. 3,351,536, Ushakoff, U.S. Pat. No. 2,455,834, and Ingram, U.S. Pat. No. 3,390,056, disclose inflatable or expandable spherical or spheroid shaped devices which are easily assembled by one man in a raft or similar craft. The basic operating principle of all three inventions is the same. Saltwater is evaporated by solar heat and allowed to condense on the inner surface of the unit. The operation will occur regardless of the sun's orientation due to the device's spherical striking surface. However, the systems are hampered by cloudy conditions.
A particular problem associated with the emergency units is the inability of such devices to produce large enough quantities on an industrial scale. Saltwater is introduced into the evaporating chamber by capillary action (Ingram) or pressure differential (Ushakoff). In Fox the saltwater is pumped directly into the evaporating chamber and a vacuum is then placed on the chamber. Due to the vacuum, the evaporating temperature of the saltwater at the surface of the water is lowered. However, the process is still hampered by a slow rate of evaporation/condensation. Enlarging the overall systems do not satisfy the demand.
More particularly, the invention concerns a desalinating solar heating apparatus which will automatically search out the sun at all times and orient itself with respect to the incident radiation from the sun. It will automatically adjust itself about mutually perpendicular gimbal axes. Therefore, the apparatus will follow the path of the sun about an azimuth and elevation angle. Several types of solar tracking systems are disclosed in the art. Trihey, U.S. Pat. No. 3,996,917, discusses several embodiments of a tracking system wherein all four photoelectric cells are mounted on a common base: yet, each sensor is shielded from the other by reflector vanes or geometric placement. Alternative forms of tracking systems are disclosed in Napoli et al. U.S. Pat. No. 4,041,307, Cashion, U.S. Pat. No. 3,421,004, and Smith U.S. Pat. No. 3,996,460. The systems operate off a photoelectric cell activated by the changing position of the sun. Unfortunately, the light striking the region of the tracking system is not defined by a sharp, definite boundary. Therefore, the sensitivity of the systems has been a constant problem. Defining at what point the photoelectric cell responds has been hampered by the inability to isolate each one within its own sheltered environment and, yet, assure consistent results among all the photocells and between consecutive tests. Recognizing this problem, Napoli, reveals the use of a lens to define a narrow region of uniform light. However, because of the limited angular movement the light source may move before bypassing this region of fine sensitivity, Napoli has included an additional set of four photoelectric cells sheltered by an overhanging flange to initially orientate the device. Essentially, the four perimeter photoelectric cells that are sheltered by the flange act as a rough tuner in orientating the device while the four inner photoelectric cells located beneath the lens act as a fine tuner. Smith discusses an adjustable shadow line system used in the general orientation of a solar device which comprises an open shadow box with movable window edges arranged around it. The adjustment of the window edges moves the shadow which falls upon the photoelectric cells thereby affecting its sensitivity. This being the only adjustment means available, there is no rough/fine distinction in controlling the sensitivity of the cells as noted in Napoli.
The problems enumerated in the foregoing are not intended to be exhaustive but rather are among many which tend to impair the effectiveness of the prior art on an industrial scale. Other noteworthy problems may also exist: however, those presented above should be sufficient to demonstrate that the present methods available to industrial users of fresh water in a saltwater environment have not been altogether satisfactory.